/**
 * Copyright 2013 Netflix, Inc.
 * <p/>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p/>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p/>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.netflix.servo.publish;

import com.netflix.servo.monitor.MonitorConfig;
import com.netflix.servo.tag.Tag;
import com.netflix.servo.tag.TagList;

import java.util.regex.Pattern;

/**
 * Filter that checks if a tag value matches a regular expression.
 */
public final class RegexMetricFilter implements MetricFilter {

  private final String tagKey;
  private final Pattern pattern;
  private final boolean matchIfMissingTag;
  private final boolean invert;

  /**
   * Creates a new regex filter.
   *
   * @param tagKey            tag to check against the pattern
   * @param pattern           pattern to check
   * @param matchIfMissingTag should metrics without the specified tag match?
   * @param invert            should the match be inverted?
   */
  public RegexMetricFilter(
      String tagKey,
      Pattern pattern,
      boolean matchIfMissingTag,
      boolean invert) {
    this.tagKey = tagKey;
    this.pattern = pattern;
    this.matchIfMissingTag = matchIfMissingTag;
    this.invert = invert;
  }

  /**
   * {@inheritDoc}
   */
  public boolean matches(MonitorConfig config) {
    String name = config.getName();
    TagList tags = config.getTags();
    String value;
    if (tagKey == null) {
      value = name;
    } else {
      Tag t = tags.getTag(tagKey);
      value = (t == null) ? null : t.getValue();
    }

    boolean match = matchIfMissingTag;
    if (value != null) {
      match = pattern.matcher(value).matches();
    }
    return match ^ invert;
  }
}
